1. Field of the Invention
The present invention relates to a vehicle ground-speed detecting apparatus.
2. Related Art Statement
There is known a vehicle ground-speed sensor which detects a ground-speed of a vehicle, that is, a speed of the vehicle relative to a road surface on which the vehicle is running, and which generates an output signal representative of the detected vehicle ground-speed. An example of the sensor is disclosed in the unexamined Japanese Patent Application laid-open under Publication No. 63(1988)-46961. The sensor is of the Doppler-effect type in which the vehicle ground-speed is detected by utilizing the Doppler effect of a wave, or of the spatial-filter type in which the vehicle ground-speed is detected by a spatial filter which detects the surface pattern (surface unevenness) of an asphalt road, a sandy road, etc.
It is possible to use respective values of the output signal from the above-indicated sensor, as true or proper vehicle ground-speeds, without subjecting those values to any processing operations. However, the output signal from the vehicle ground-speed sensor may largely be deviated. Thus, those proper vehicle ground-speed values may be inaccurate.